Check your credit card. If it's from American Express, then you'll want to listen up. The company has recently admitted a data breach that it's been hiding for two years.

American Express explained in a letter to the California attorney general's office that it "became aware that a third-party service provider engaged by numerous merchants experienced unauthorized access to its system."

LONDON, ENGLAND - AUGUST 19: A detail of the Ashley Madison website on August 19, 2015 in London, England. Hackers who stole customer information from the cheating site AshleyMadison.com dumped 9.7 gigabytes of data to the dark web on Tuesday fulfilling a threat to release sensitive information including account details, log-ins and credit card details, if Avid Life Media, the owner of the website didn't take Ashley Madison.com offline permanently. (Photo by Carl Court/Getty Images)

Katherine Archuleta, director of the U.S. Office of Personnel Management (OPM), speaks during a House Oversight and Government Reform Committee hearing on the OPM data breach in Washington, D.C., U.S., on Wednesday, June 24, 2015. U.S. senators said yesterday they doubt the government's personnel office understands the breadth of a computer hack that exposed the records of more than 4 million federal workers, or that the agency can stop another breach. Photographer: Andrew Harrer/Bloomberg via Getty Images

WASHINGTON, DC - JUNE 05: The entrance to the Theodore Roosevelt Federal Building that houses the Office of Personnel Management headquarters is shown June 5, 2015 in Washington, DC. U.S. investigators have said that at least four million current and former federal employees might have had their personal information stolen by Chinese hackers. (Photo by Mark Wilson/Getty Images)

SCHAUMBURG, IL - AUGUST 04: A statue of a horse stands at the entrance to a P.F. Chang's restaurant on August 4, 2014 in Schaumburg, Illinois. P.F. Chang's China Bistro Ltd. said today that the company experienced a data breach involving customers' credit and debit card information which affected 33 restaurants in 16 states, including the Schaumburg, Illinois location. (Photo by Scott Olson/Getty Images)

COLMA, CA - APRIL 18: Customers enter a Michaels art and crafts store on April 18, 2014 in Colma, California. Michaels, the largest arts and crafts chain in the U.S., announced that an estimated 2.6 million cards used at its stores across the country may have been affected by a security breach. Aaron Brothers, a subsidiary of Michaels, was also affected by the breach. (Photo by Justin Sullivan/Getty Images)

CORAL GABLES, FL - FEBRUARY 28: A checkout keypad is seen at a Sears store on February 28, 2014 in Coral Gables, Florida.

According to reports the U.S. Secret Service is investigating a possible digital attack at Sears Holdings Corp. (Photo by Joe Raedle/Getty Images)

A couple of shoppers leave a Target store on a rainy afternoon in Alhambra, California on December19, 2013, as the US retail giant said some 40 million customers may have had bank card data compromised by hackers who broke into its database as holiday shopping got underway. Target said there had been 'unauthorized access' to its payment system in US stores affecting credit and debit cards with approximately 40 million credit and debit cards possibly affected by the breach between November 27 and December 15, the company said in a statement. AFP PHOTO / Frederic J. Brown (Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)

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Since originally filing this notification with the attorney general's office, the company has revised its statement, claiming that a "merchant," rather than a "third-party service" was actually the victim of the breach. But, it's important to note that in both statements, American Express affirmed that none of its owned systems had been tampered with.

Should you be concerned? Well, it's tough to say how large the breach was, and what actually happened. Thus far, American Express has remained tight-lipped about the number of card members who were affected. And, the company's story seems to change periodically, which causes some to speculate over a possible cover-up.

Regardless, this story just goes to show how vulnerable we all are to having our personal information stolen.